Visible-Light-Induced Photocatalyst-Free Aerobic Hydroxyazidations of Indoles: A Highly Regioselective and Stereoselective Synthesis of trans-2-Azidoindolin-3-ols.

A visible-light-promoted aerobic hydroxyazidation of indole derivatives with TMSN3 is described. The reaction proceeded under photocatalyst-free conditions to furnish trans-2-azidoindolin-3-ols with high regioselectivity and stereoselectivity. The protocol is operationally simple, and the starting materials (e.g., 1-(pyrimidin-2-yl) indoles, azidotrimethylsilane, and air) are readily available. The proposed mechanism in which substrates act as photocatalysts upon excitation using blue light-emitting diodes (LEDs) was supported by experimental studies.